Detecting impaired heart mechanical performance

ABSTRACT

A pressure-sensitive device contacts the skin of a patient near an artery noninvasively to provide a signal representative of systemic arterial blood pressure both before and after a Valsalva Manoeuvre. This blood pressure signal is differentiated, and the changes in amplitude before and during the Valsalva Manoeuvre detected to indicate potential left ventricle failure when the change is to less than a predetermined value. Signals representative of pulse pressure, the mean systemic arterial blood pressure, heart rate and left ventricular ejection time are also provided to facilitate detection of impaired mechanical performance of the heart.

United States Patent McIntyre 1*Sept. 30, 1975 [54] DETECTING IMPAIRED HEART 3,698,382 10/1972 Howell 128/205 V MECHANICAL PERFORMANCE 3,776,221 12/1973 Mclntyre 128/105 R [76] Inventor: Kevin M. McIntyre, 1 l 1 Perkins St., THER PUBLICATIONS Jamalca Plum Mass 02130 George et al., Medical Research Engineering," 4th Notice: The portion of the term of this w 1967, PP-

patent subsequent to Dec. 4, 1990, has been disclaimed. Primary Examiner-Wil1iam E. Kamm [22] Filed: Oct. 3, 1973 Atturnqv, Agent, or FzrmCharles Hieken; Jerry Cohen [21] Appl. No.: 403,202

Related US. Application Data [57] ABSTRACT Continuation-impart 0f N1 pril 2, A pressure-sensitive device contacts the skin of a pa- 1971* tient near an artery noninvasively to provide a signal representative of systemic arterial blood pressure both [52] US. Cl l28/2.05 R before and after a valsalva Manoeuvrc This blood [51] It'll. Cl Afilb 5/02 pressure Signal is differentiated, and the changs in [58] held of 128/205 amplitude before and during the Valsalva Manoeuvre 128/205 Gt 205 ML 205 detected to indicate potential left ventricle failure R when the change is to less than a predetermined value.

I Signals representative of pulse pressure, the mean sys- [561 References C'ted temic arterial blood pressure, heart rate and left ven- UNITED STATES PATENTS tricular ejection time are also provided to facilitate de- 3.1s4.0ee 10/1964 Grindheim et a1. 128/105 P tection of impaired mechanical Performance of the 3,412,729 11/1968 Smith, Jr 128/205 R heart.

3,570,474 3/1971 Jonson 128/2105 V 3,602,213 8/1971 Howell et a1. 128/205 P 6 Clams, 8 Drawmg Flgures COMPUTER ANALYSIS CONTROL RECOVERY MEANS OR\ HEART RATE LV EJECI. TIME 11 RI PULSE PRESS. w OR! MEAN PRESS PULSE I Pickup PEAK PREss g SELECTOR sP1-1YeMo TRANS AMPLIFIER WRITE our ,m

MANOMETER DUCER MEANS MEANs AND L VF l-o l2 IMPEDANCE PLETHYSMO 22 23 GRAPH I6 COMPUTER ANALYSIS DER'VAT'VE CONTROL RECOVERY MAx dp/dt MEANS DIFFERENTIATOR (a CD=QRP US. Patent FIG. 46'

Sept. 30,1975 Sheet 3 of 3 STRAIN RELEASE I I III :IZI

RECOVERY PERIPHERAL ARTERIAL PULSE dp/dt OF PERIPHERAL ARTERIAL PULSE PERIPHERAL ARTERIAL PULSE dp/di OF PERIPHERAL ARTERIAL PULSE I I I I I x I l I I I I I I I I I I I I I LVF), I MI 1 ADJUST SENSITIVITY TO BRING CONTROL dp/dI IN CONTACT WITH BOUNDARIES OF 'CONTROL LEVEL PERFORM VALSALVA, RECORDING dp/df @READ TRACING ACCORDING TO AMPLITUDE OF STRAIN PHASE ISI DERIVATIVE OF PERIPH. PULSE TRACING CONTROL vs. STRAIN IN VALSALVA MANEUVER DETECTING IMPAIRED HEART MECHANICAL PERFORMANCE CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation in part of my copending application, Ser. No. 130,572 filed Apr. 2, 197i, and now US. Pat. No. 3,776,221, dated Dec. 4, 1973.

BACKGROUND OF THE INVENTION The present invention relates in general to detecting impaired mechanical performance of the heart and/or cardiac failure, and more particularly concerns novel apparatus and techniques for detecting such potential impairment in a reliable manner through external measurements.

Since the introduction of aortic valvotomy, the assessment of aortic valve disease has become increasingly important. One approach to such an assessment involves studying recorded arterial pressure pulse tracings. Stenosis is the narrowing of a blood passage, such as the pulmonary artery or aortic valve. One approach to studying stenosis is the so-called Valsalva Manoeuvre. The patients blood pressure is recorded prior to holding his breath. Then the patient holds his breath and releases it while recording continues.

Reference is made to an article in 19 BRITISH HEART JOURNAL 525-3l( 1957) entitled THE VAL- SALVA MANOEUVRE IN AORTIC VALVE DISEASE by Doyle and Neilson, a copy of which is in the file history of the application. The article states that neither systolic upstroke time nor pulse pressure alone correlates well with the severity of stenosis and that the shape of the pulse derived during Valsalva Manoeuvre is an unreliable guide to the relative dominance of stenosis or incompetence. That article concludes that variations in pulse pressure during the Valsalva Manoeuvre or in atrial fibrillation and variations of upstroke time in the same pulses do have a linear relationship to the severity of stenosis when stenosis is present alone.

It is an important object of this invention to provide improved techniques for detecting left ventricular impairment.

It is a further object of the invention to achieve the preceding object with techniques that permit detection by relatively unskilled personnel.

SUMMARY OF THE INVENTION According to the invention, the time derivative of the systemic arterial pulse pressure is established at a control level in the subject patient. Then the patient performs a straining manoeuvre, such as a Valsalva manoeuvre, while recording the time derivative of the systemic arterial pulse pressure signal. Preferably, the systemic arterial pulse pressure, mean pressure, heart rate and left ventricular ejection time are also established and may be interpreted so that the presence or absence of impairment in the performance of the left ventricle may be detected. Specifically, the time derivative of systemic arterial pressure responds in a characteristic fashion in the presence of heart impairment; the other parameters are useful in defining the expected normal response of the time derivative of this pressure. Diminution of said time derivative relative to a control during the manoeuvre and/or increase of said time derivative relative to a control after said manoeuvre are detected and evaluated in light of the other parameters as determinants of probable mechanical impairment.

Numerous other features, objects and advantages of the invention will become apparent from the following specification when read in connection with the accompanying drawing in which:

BRIEF DESCRIPTION OF THE DRAWING FIG, 1 is a graphical representation of stroke volume as a function of end-diastolic pressure of the left ventricle during a Valsalva manoeuvre helpful in understanding the phenomena with which the invention is associated;

FIG. 2 is a block diagram illustrating the logical arrangement of a system according to the invention which includes means for detecting left ventricle me chanical impairment;

FIGS. 3 and 5 are graphical representations of time derivative of pressure waveforms helpful in under standing the operation of the invention; and

FIGS. 4A and 4C are graphical representations of typical peripheral arterial pulse waveforms generated during Valsalva Manoeuvre in the presence and absence, respectively, of heart impairment and FIGS. 48 and 4D are graphical representations of time derivatives of the 4A and 4C waveforms, respectively.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference now to the drawing, and more particularly FIG. 1 thereof, there is shown a graphical representation of stroke volume as a function of enddiastolic pressure in the left ventricle during a Valsalva manoeuvre. Curve 11 illustrates this relationship for a normal left ventricle. Point 1 represents the normal stroke volume and end-diastolic pressure immediately prior to the patient holding his breath. As the patient holds his breath and makes a forceful expiratory effort without allowing air to escape from his lungs (equivalent to straining at stool), both pressure and stroke vol ume decrease along curve 11 to point 2 when the patient releases his breath. Stroke volume and enddiastolic pressure then begin to increase rapidly until point 3 is reached. This analysis indicates that the time derivative of the pressure signal ofa healthy patient will increase significantly when he releases his breath. Since other changes occur during the Valsalva manoeuvre which may on occasion independently influence the response of stroke volume and the time derivative of pressure, the influence of such changes as heart rate and left ventricular ejection time are also measured.

Curve 12 is the curve illustrating the relationship between stroke volume and end-diastolic pressure of the left ventricle of a person having left ventricle mechanical impairment. Point 1 is just before the patient holds his breath. He then makes a forceful expiratory effort without allowing air to escape. This initial pressure (EDP) is somewhat higher and the initial stroke volume (SV) usually somewhat lower than for a normal person, then decreases to point 2' shortly before the breath is released. When breath is released, the blood which was prevented from returning to the heart does so at an increased rate, causing an increase in end-diastolic pressure. During the positive pressure phase, pressure generated in the chest exceeds the pressure of returning blood.

In a patient with mechanical impairment of the heart, no increase in stroke volume occurs with a rise in enddiastolic pressure (position 3'), and this is detectable by a failure of the time derivative of the systemic arterial pulse pressure to increase. The range of changes which occur are acceptable in the individual patient depending to some extent on changes in other parameters, such as heart rate and left ventricular ejection time.

Referring to FIG. 2, there is shown a block diagram illustrating the logical arrangement of a system according to the invention. Basically the invention senses a recovery derivative signal to indicate left ventricular impairment when this amplitude is equal to or less than a predetermined value. To this end the invention may include a number of different sources of a pressure signal. One such source may be a piezoelectric pulse pickup 11, an impedance plethysmograph 12 or a sphygmomanometer 13 whose pressure signal is converted by transducer 14 into an electrical signal that is delivered to amplifier means 15. Each of these sources is a pressure sensitive means noninvasive of the human body and derives a signal from contact with the skin surface near an artery. Amplifier means 15 includes means for amplifying one of the selected pressure signals and providing the amplified pressure signal to differentiator 16 that provides a differentiated pressure signal for analysis.

The apparatus also may include computer analysis control recovery means 21, which may receive a pressure signal from amplifier means 15 and a computer analysis control recovery means 22 for responding to the time derivative pressure signal provided by differentiator 16. Computer analysis control recovery means 21 preferably responds to heart rate, systemic arterial pulse pressure, peak systemic pressure, systemic mean pressure and left ventricular ejection time so that changes in these latter parameters may be used to more accurately define the predicted normal range for the time derivative of systemic arterial pulse and to provide a 1 signal to indicate a condition consistent with left ventricular mechanical impairment and a 2 signal to indicate a signal inconsistent with left ventricular mechanical impairment. Similarly computer analysis control recovery means 22 provides a 1 signal consistent with left ventricular failure and a 2 signal consistent with no failure. These 1 signals are applied to an AND gate 23 which provides an output to indicate left ventricular mechanical impairment, and the 2 outputs are applied to the legs of a second AND gate 24 that provides an output to indicate no ventricular failure.

The invention may also comprise write-out means 25, which may be a graphical recorder whose output may be manually analyzed or appear on calibrated paper that automatically displays the presence or absence of mechanical impairment.

Referring to FIG. 3, there is shown three pairs of I than level 34, such as that of pulse pair 35, there is no left ventricular impairment.

If the height is less than level 34, such as that of pulse pair 33, then the heart rate signals, systemic pulse pressure signals, peak systemic pressure signals, mean systemic pressure signals and left ventricular ejection time signals are subjected to further computer analysis to determine the extent to which certain of these parameters may independently alter the time derivative signal. For example, if changes in heart rate, the systemic arterial pulse pressure, mean pressure, systolic peak pressure and left ventricular ejection time are greater than a predetermined level, a second independent reanalysis of the pressure derivative signal is provided which takes into account the possible influence of changes in the latter parameters on the time derivative of pressure. Such an analysis is unlikely to be required in routine use but will improve the accuracy of the instrument.

Details of the various elements of the system represented by the boxes have not been described to avoid obscuring the principles of this invention and because such elements are known to those having ordinary skill in the signal analysis art.

For example, heart rate is readily determined by a digital counter whose count is compared by known techniques with a predetermined reference count equal to a control heart rate. The other two pressures may be readily determined by analog comparison techniques or by first converting these signals to digital values and making the comparison digitally.

While the above embodiment of the invention contemplates utilizing both derivatives and other signals in sensing for mechanical impairment of the heart, the derivative signal itself provided by differentiator 16 is most significant. Those skilled in the art might also determine the derivative by analyzing the pressure signal.

An advantage of differentiating before analyzing is that shifts in d-c pressure levels are essentially removed so that the resultant output signal waveform clearly represents a manifestation of the change in rate of pressure as a function of time to facilitate diagnosing left ventricular impairment.

Referring to FIGS. 4A-4D, phenomena involved according to another important aspect of the invention may be explained. The single curves of each of these figures have a common time x-axis taken over a period encompassing the initiation and release of strain pursuant to a Valsalva manoeuvre, recovery therefrom and periods just prior to initiation of strain and following the beginning of recovery. FIGS. 4A and 4C have curves 1 1 1 and 1 12, respectively, which exemplify typical peripheral arterial pulse measurements for patients with normal and impaired hearts, respectively. During the time period A, the normal and impaired hearts produce similar pulse measurements. During the following period B, which includes at least the latter half of the manoeuvre, the normal heart produces progressively and markedly reduced pulse amplitudes relative to the amplitude initially induced during period A by the onset of strain. In the next subsequent period C, the normal heart produces at least some pulse peaks higher than the peaks measured before strain onset in period A. The impaired heart produces and maintains the new higher amplitude throughout the strain time with little or no diminution in period B. The recovery transition of the impaired heart in period C is unaccompanied by significant higher peaks compared to those preceding strain in period A.

Waveforms 121 in FIG. 4B and 122 in FIG. 4D are time derivatives of curves 111 in FIG. 4A and 112 in FIG. 4C, respectively. Diminution of peak height of 121 in period B for the normal heart and the essential absence of such diminution of peak height of curve 122 for the impaired heart provides a highly sensitive determinant of impairment, usable in addition to or in lieu of comparative behavior in periods A and C as described above in connection with FIGS. 1, 2 and 3.

The apparatus cited above in connection with FIG. 2 may be employed. The same patient preparation, apparatus manipulation and data acquisition techniques may be used. The data evaluation taught above in connection with FIG. 3 is however substituted or supplemented as follows.

Referring to FIG. 5, there is shown three pairs of time derivative pulses that might be recorded during the course of a Valsalva manoeuvre. The first pair of pulses 131 occurs prior to holding the breath. The gain of amplifier means (FIG. 2) is then adjusted so that the peak of the time derivative pressure waveform just reaches or slightly exceeds control line 132 with its baseline adjusted to 131A. During the manoeuvre if the pulses have a height such as that of pair 133, that is about the same as pulses 131, left ventricular mechanical impairment is probable. If they have a substantially lower height such as that of pulse pair 135, there is no left ventricular impairment. A control level 134 may be established. If the peak height is greater than level 134, such as that of pulse pair 133, then the heart rate signals, systemic pulse pressure signals, peak systemic pressure signals, mean systemic pressure signals and left ventricular ejection time signals are subjected to further computer analysis to determine the extent to which certain of these parameters may independently alter the time derivative signal. For example, if changes in heart rate, the systemic arterial pulse pressure, mean pressure, systolic peak pressure and left ventricular ejection time are greater than a predetermined level, a second independent reanalysis of the pressure derivative signal is provided which takes into account the possible influence of changes in the latter parameters on the time derivative of pressure. Such an analysis is unlikely to be required in routine use but will improve the accuracy of the instrument.

There has been described novel apparatus and techniques for facilitating the detection of mechanical heart impairment by relatively unskilled personnel. It is evident that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments disclosed herein without departing from the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and limited solely by the spirit and scope of the appended claims.

What is claimed is:

1. A method of detecting mechanical heart impairment which method includes the steps of,

noninvasively providing a blood. pressure signal representative of blood pressure by placing pressure sensitive means in contact with the skin of a patient near an artery,

differentiating said blood pressure signal,

subjecting said patient whose blood pressure is characterized by said pressure signal to a heart straining manoeuvre,

detecting the change in the amplitude of the differentiated pressure signal after initiating said straining manoeuvre from its amplitude before said manoeuvre,

and determining a probable mechanical impairment of the heart when the amplitude is not changed to a predetermined extent.

2. A method of detecting mechanical heart impairment in accordance with claim 1 wherein said detection of change in amplitude of the differentiated pressure signal after initiation of said manoeuvre is made with respect to a diminution, if any, of said amplitude before completion of said manoeuvre.

3. A method of detecting mechanical heart impairment in accordance with claim 2 wherein said heart straining manoeuvre is a Valsalva manoeuvre.

4. A method of detecting mechanical heart impairment in accordance with claim 3 wherein said Valsalva manoeuvre is involuntarily induced in said patient.

5. A method of detecting mechanical heart impairment in accordance with claim 2 and further including the steps of providing signals representative of systemic peak pressure, systemic mean pressure, heart rate, and left ventrical ejection time both before and after said manoeuvre and sensing the differences between respective signals before and during said manoeuvre.

6. A method of detecting mechanical heart impairment in accordance with claim 2 which method inclucles the steps of,

recording the differentiated blood pressure signal so that its peak amplitude before said manoeuvre is related to a predetermined control line,

and observing the amplitude of said differentiated blood pressure signal during said manoeuvre relative to a predetermined normal limit line spaced below said control line to determine potential mechanical impairment when the peak amplitude during said manoeuvre is above the normal limit line and no mechanical impairment when below said normal limit line. 

1. A method of detecting mechanical heart impairment which method includes the steps of, noninvasively providing a blood pressure signal representative of blood pressure by placing pressure sensitive means in contact with the skin of a patient near an artery, differentiating said blood pressure signal, subjecting said patient whose blood pressure is characterized by said pressure signal to a heart straining manoeuvre, detecting the change in the amplitude of the differentiated pressure signal after initiating said straining manoeuvre from its amplitude before said manoeuvre, and determining a probable mechanical impairment of the heart when the amplitude is not changed to a predetermined extent.
 2. A method of detecting mechanical heart impairment in accordance with claim 1 wherein said detection of change in amplitude of the differentiated pressure signal after initiation of said manoeuvre is made with respect to a diminution, if any, of said amplitude before completion of said manoeuvre.
 3. A method of detecting mechanical heart impairment in accordance with claim 2 wherein said heart straining manoeuvre is a Valsalva manoeuvre.
 4. A method of detecting mechanical heart impairment in accordance with claim 3 wherein said Valsalva manoeuvre is involuntarily induced in said patient.
 5. A method of detecting mechanical heart impairment in accordance with claim 2 and further including the steps of providing signals representative of systemic peak pressure, systemic mean pressure, heart rate, and left ventrical ejection time both before and after said manoeuvre and sensing the differences between respective signals before and during said manoeuvre.
 6. A method of detecting mechanical heart impairment in accordance with claim 2 which method includes the steps of, recording the differentiated blood pressure signal so that its peak amplitude before said manoeuvre is related to a predetermined control line, and obsErving the amplitude of said differentiated blood pressure signal during said manoeuvre relative to a predetermined normal limit line spaced below said control line to determine potential mechanical impairment when the peak amplitude during said manoeuvre is above the normal limit line and no mechanical impairment when below said normal limit line. 